This is a request for an NIMH Scientist Development Award (K01) to provide training and research experience in a broad range of approaches aimed at studying pediatric bipolar disorder. The candidate's goal is to foster his development as an independent investigator and to apply the knowledge acquired during this training to ongoing research. The candidate is proposing a comprehensive, systematic, portfolio of research designed to examine the validity and heterogeneity of pediatric bipolar disorder using data from several large existing cross-sectional and longitudinal clinical research databases. The studies that created these data sets have comprehensively assessed youth, and their first degree relatives on multiple, nonoverlapping domains of functioning. The overarching aim of the proposed research is to determine whether pediatric onset bipolar disorder is a valid entity and if so, what are the core features of the disorder and its boundaries from other disorders. This aim will be carried out with psychometric analyses that will identify the particular symptoms of bipolar disorder that are most efficient in making the diagnosis in children. Latent class analyses will be conducted to identify subforms of bipolar disorder based upon symptom course and expression that are not biased by diagnostic preconceptions. Once defined, the validity of these subtypes will be tested in examinations of their clinical correlates, course and stability, familiality, and differentiation from attention-deficit hyperactivity disorder. To further characterize the putative subtypes of bipolar disorder, the candidate will conduct path analyses of the onset of psychiatric comorbidity in order to identify different trajectories that may lead to the disorder in children. Consistent with research of the etiology of other childhood psychopathology, the candidate proposes to study the family environment, the climate surrounding early development, the in utero environment, and individual behavioral traits as potential risk factors for pediatric bipolar disorder. The candidate has selected mentors and consultants who will provide him with the opportunity to augment the skills obtained during his training in epidemiology with new statistical and data analytic methods needed to carry out the specific aims of the proposed research. This systematic approach of research and training may lead to advances in early intervention and prevention of pediatric bipolar disorder.